(+)-cis - 1,3-dibenzyl-hexahydro-1h-thieno-(3,4-d)imidazoles - 2,4-dione, and process for tis preparation

ABSTRACT

RACEMIC AND (+)-CIS - 1,3 - DIBENZYL-HEXAHYDRO-1H THEINO (3,4-D: IMIDAZOLE - 2,4-DIONE AND VARIOUS INTERMEDIATES, PREPARED FROM THE CORRESPONDING CIS-1,3-DIBENZYL-HEXAHYDRO-1H-FURO(3,4-D)IMIDAZOLE,2,4-DIOME, ARE DESCRIBED. THE END PRODUCTS ARE VALUABLE INTERMEDIATES IN THE SYNTHESIS OF (+)-BIOTIN, AS WELL AS DERIVATIVES AND RELATED PRODUCTS THEREOF. PROCESSES FOR THE SYNTHESIS OF (+)-BIOTIN ARE ALSO DESCRIBED.

United States Patent 3,740,416 (+)-CIS 1,S-DIBENZYL-HEXAHYDRO-lH-THIENO- [3,4-d]lMIDAZOLES 2,4-DIONE, AND PROCESS FOR ITS PREPARATION Max Gerecke, Reinach, Switzerland, and Jean Pierre 5 Zimmermann, Saint Louis, France, assignors to Holimann-La Roche, Inc., Nutley, NJ. No Drawing. Filed Nov. 17, 1970, Ser. No. 90,477 Claims priority, application Switzerland, Nov. 29, 1969, 17,773/69 Int. Cl. C07d 63/02 U.S. Cl. 260309.7

2 Claims ABSTRACT OF THE DISCLOSURE Racemic and )-cis 1,3 dibenzyl-hexahydro-IH- thieno[3,4-d]imidazole 2,4-dione and various intermediates, prepared from the corresponding cis-1,3-dibenzyl-hexahydro-lH-furo[3,4-d]imidazole-2,4-dione, are described. The end products are valuable intermediates in the synthesis of (+)-biotin, as well as derivatives and related products thereof. Processes for the synthesis of (+)-biotin are also described.

BRIEF SUMMARY OF THE INVENTION The invention relates to the optically active thiolactone of the formula 2 R- 1 3N-R A 6a 321 wherein the rings A and B are cis-linked and R is benzyl.

In another aspect, the invention relates to optically active compounds of the following formulas, of which the Formulas III, IV, IX, X, XII and XIII have the absolute configuration of biotin in the positions 3a and 6a and the Formulas V, VI, XIV, XV and XVI have the ab- XII XIII

XIV

Patented June 19., 1973 CODE CHaOR;

and

XVI

wherein R is as previously described; R is lower alkyl of 1-4 carbon atoms, and R is benzyl or lower alkyl of 1-4 carbon atoms.

In still another aspect, the invention relates to processes for the preparation of )-biotin.

DETAILED DESCRIPTION OF THE INVENTION The invention relates to the optically active (+)-thiolactone of the formula wherein rings A and B are cis-linked, and R is as described above, is reacted at an elevated temperature with a salt of a thio derivative of a carboxylic acid. For the preparation wherein R is benzyl, with cholesterol or with cyclohexanol into the corresponding half-esters of the formulas wherein R is as previously described and R is cyclohexyl or chloesteryl, separating the diastereomeric cholesterol half-esters from each other 'by fractional crystallization of their triethylamine salts or resolving the enantiomeric cyclohexyl half-esters from each other by fractional crystallization of their ephedrine salts, and converting the salts of the desired antipode, i.e., the antipode, or the desired diastereomer, i.e., the (+)-diastereomer, thus obtained into the (+)-lactone of Formula a.

The conversion of the trione of Formula a by means of cholesterol or by means of cyclohexanol into the corresponding half-esters of Formulas b and c is expediently carried out in an inert organic solvent, preferably in an aromatic hydrocarbon, and at an elevated temperature, preferably at the reflux temperature of the reaction mixture.

The separation of the racemic or diastereomeric halfesters of Formulas b and c with triethylamine or with ephedrine is expediently effected in a lower alkanol such as ethanol or isopropanol, or in a lower ketone such as acetone, at a temperature in the range of about 40 C. to about the boiling temperature of the reaction mixture.

The salts of the desired antipode or the desired diastereomer thus obtained can be directly converted into of (+)-biotin, the carboxybutyl side-chain is introduced to the (+)-thiolactone and the benzyl groups are split 01f.

The (+)-thiolactone is understood to be that antipode which is dextrorotatory in chloroform.

The racemic lactone of the Formula II used as starting material is a known substance and can be prepared according to known methods. For example, it can be obtained by reacting cis-bis-benzylaminosuccinic acid with phosgene in the presence of alkali, treating the reaction product with a dehydrating agent and, thereafter reducing the resulting product.

The optically active (+)-lactone which can also be used as the starting material, is a new substance and can, for example, be prepared by converting the trione of the formula 0 R- N-R the +)-1actone of Formula II by means of lithium borohydride in an inert organic solvent.

If a racemic lactone of Formula II is used as the starting material in the process of the invention, there is obtained the racemic thiolactone of Formula I, and, when the optically active (+)-lactone of Formula II is used as the starting material, there is obtained the optically active (+)-thiolactone of Formula I.

The reaction of the lactone of Formula II, that is, both the racemate and the optically active (+)-form, with a salt of a thio derivative of a carboxylic acid is expediently effected in an inert organic solvent and at a temperature in the range of about 100 C. to about 200 C., preferably in the range of about 140 C. to about 185 C.

As the solvent there are expediently used high-boiling solvents, especially high-boiling amides, tert. amines, ethers, and the like. Exemplary of such solvents are diethylaniline, collidine, lutidine, phenyl ethyl ether and,

I preferably, dimethylacetamide, dimethylformamide, quinoline, and the like. However, solvents with a lower boiling point such as, perhaps, carbon disulfide or cyclic ethers such as tetrahydrofuran or dioxane, or tert. amines such as pyridine, triethylamine, and the like, can also be 7 used, in such case the reaction expediently is carried out under pressure.

The reaction can also be carried out without solvent in the melt.

The reaction is expediently carried out under an atmosphere of an inert gas, for example, under nitrogen.

As salts of a thio derivative of a carboxylic acid, there can be used salts of strong bases, for example, alkali or alkaline earth metal salts and, preferably, sodium or potassium salts. The carboxylic acid moiety is not critical. Both aliphatic and aromatic carboxylic acids can be used as long as they are stable above C. Preferred salts of thio derivatives of carboxylic acids are the sodium and potassium salts of thioacetic acid, thiobenzoic acid,

and the like. Potassium thioacetate is particularly preferred.

The conversion of the optically active (+)-thiolactone into (+)-biotin is carried out in accordance with reaction Schemes I, II and In, which follow. 5

SCHEME 1 R-N A N-R RN NR XMgCHzCHzCHrORt I B B on CHzOR; I III Hz0 l/ o 0 II I RN A N-R R B H2 cat. B

onion, onzort iv v HBr 0 0 00R! A R--N N-R AOH R-N N-R COORi I O i O COOR;

VI VII HBr/ 1/ HN N-H C O OH -biotni VIII In Formulas I, III and IV, rings A and B are cis-linked. In Formulas V, VI, VII and VIII, the hydrogen atoms in positions 6a, 3a and 4 are cis-located. The R in each case is benzyl, R is lower alkyl With 1 to 4 carbon atoms and X is chlorine or bromine. A is an alkali metal atom. The optically active compounds of Formulas III, IV, V and VI are new compounds, and as such are part of this invention.

In Scheme 1, the +)-thiolactone of Formula I is converted by a Grignard reaction into the optically active compound of Formula HI. The conversion of this compound into that of Formula IV is effected :by means of a dehydrating agent, for example, glacial acetic acid, or a dilute mineral acid, such as dilute sulfuric acid. The compound of Formula IV is converted by catalytic hydrogenation using, for example, Raney-nickel as the catalyst into the compound of Formula V. The alkoxy groups are split from this compound by, for example, hydrobromic acid to yield the compound of Formula VI. The compound of Formula VI is converted by treatment with an alkali metal dialkyl malonate such as sodium diethyl malonate into 75 the compound of Formula VII. The compound of Formula VII is saponified and, after decarboxylation and debenzylation, there is obtained (+)-biotin of Formula VIII.

SCHEME II 1) XMgClLCHzCHzCHzMgX 2) 002 IX -H2 0/ i/ o RN NR A H; cat.

coon

o R-N N-R coon XI HBr o A H- NH 00011 (+)-biotin VIII In Formulas 1, IX and X, rings A and B are cis-linked. In Formulas XI and VIII, the hydrogen atoms in positions 6a, 3a and 4 are cis-located. The R is benzyl and X is chlorine or bromine. The optically active compounds of Formulas IX and X are new compounds, and as such are part of this invention.

In Scheme 11, the (+)-thiolactone of Formula I is converted by a Grignard reaction and subsequent treatment with carbon dioxide into the optically active compound of Formula IX. The conversion of the compound of Formula IX into that of Formula X is etfected by means of a dehydrating agent such as, for example, glacial acetic or a dilute mineral acid, for example, dilute sulfuric acid. The compound of Formula X is converted by catalytic hydrogenation using, for example, Raney-nickel as the catalyst into the compound of Formula XI. By debenzylation of the compound of Formula XI, there is obtained (+)-biotin of Formula VIII.

SCHEME III A R-N N-R A XMgomomomomom LB L R-N NR I A I onion, s/ XII -H20 R-N N-R l A Hg-F cat.

B L MCHzORZ RN N-R L kA/OH ORQ xrv 0 0 II II RN N-R R-N NR NaCN CHQBI L s s cm xv XVI HBr H-N NH coon vnI (+)biotin In Formulas I, X11 and XIII, rings A and B are cislinked. In Formulas XIV, XV, XVI and VIII, the hydrogen atoms in positions 6a, 3a and 4 are cis-located. The R is benzyl, R is benzyl or lower alkyl with 1 to 4 carbon atoms and X is chlorine or bromine. The optically active compounds of Formulas XII, XIII, XIV, XV and XVI are new compounds, and as such are part of this invention.

In Scheme III, the (+)-thiolactone of Formula I is converted by means of a Grignard reaction into the optically active compound of Formula XII. The conversion of the compound of Formula XII into that of Formula XIH is effected utilizing a dehydrating agent, for example, glacial acetic or a dilute mineral acid such as sulfuric acid.

The compound of Formula XIII is converted by catalytic hydrogenation using, for example, Raney-nickel as the catalyst, into the compound of Formula XIV. The conversion of the compound of Formula XIV into the compound of Formula XV is eflected by treatment with hydrobromic acid in glacial acetic. The transformation of the compound of Formula XV into the compound of Formula XVI is effected by means of an alkali metal cyanide, for example, sodium cyanide. The compound of Formula XVI is converted into (+)-biotin of Formula VIII by saponification and debenzylation.

The following examples further illustrate the invention. All temperatures are in degrees centigrade, unless otherwise mentioned.

EXAMPLE 1 Preparation of -cis-1,3-dibenzyl-hexahydro-1H- thieno 3,4-d] imidazole-2,4-dione 50 g. of (+)-cis-1,3-dibenzyl-hexahydro-1H-furo[3,4- d]imidazole-2,4-dione and 20 g. of potassium thioacetate are stirred in 50 ml. of dimethylacetamide under nitrogen for 30 minutes at 150 C. The reaction mixture is cooled and partitioned between water and benzene. The aqueous phase is once more extracted with benzene, and the benzene phases are once more washed with water. After evaporation of the organic extracts, the residue is recrystallized from isopropanol to yield about 48.4 g. of (+)-cis-1,3-dibenzy1 hexahydro 1H thieno[3,4-d] imidazole-2,4-dione having a melting point of -127 C.; [a] =|9O.4 to +92.2 (c.=l in chloroform).

The (-l-) cis-l,3-dibenzyl-hexahydro-lH-furo[3,4-d] imidazole-2,4-dione used as the starting material can be prepared as follows:

77.5 g. of cholesterol are suspended in 500 ml. of henzene. To remove the moisture, ml. of benzene are removed by distillation. 45 g. of cis-1,3-dibenzyl-hexahydro-lH-furo[3,4-d]imidazole-2,4,6-trione are then added. The resulting mixture is boiled at reflux for 18 hours, and then cooled and concentrated under vacuum. To remove the benzene, the residue is twice dissolved in 50 ml. of acetone and the solvent in each case is removed by distillation. The residue is dissolved in 450 ml. of acetone at 40 C. and treated with 14.9 g. of triethylamine, whereby the temperature rises to 50 C. The mixture is allowed to cool slowly to 23 C., and the crystals are filtered (40 g.). After recrystallization from 650 ml. of ethanol, there are obtained 30 g. of pure (+)-cis-1,3-dibenzyl-5-(3'- cholesteryloxycarbonyl) 2 oxo 4 imidazolidine-carboxylic acid triethylamiue salt; [a] 1=+8.4- (c.=5.0 in CHCl 5.9 g. of potassium borohydride and 6.075 g. of lithium chloride are stirred overnight in 73 ml. of tetrahydrofuran under nitrogen. The resulting mixture is heated to 30 to 35 C. and a solution containing 30 g. of (+)-cis-1,3-dibenzyl 5 (3 cholesteryloxycarbonyl) 2 oxo-4- imidazolidine-carboxylic acid triethylamine salt in m1. of tetrahydrofuran is added dropwise with stirring over a period of 2 hours at a temperature of at most 50 C. Subsequently, the mixture is boiled at reflux for 2 hours and 65 ml. of tetrahydrofuran are then removed by distillation at normal pressure. 73 ml. of methanol are slowly added to the residue, which is then boiled at reflux for /2 hour. Thereafter, 18.25 ml. of concentrated hydrochloric acid are added, and the mixture is boiled at reflux for an additional 30 minutes. Then, the solvent is removed by distillation at normal pressure to a volume of 75 ml. 250 ml. of methanol are added. The mixture is boiled at reflux for 15 minutes and allowed to stand overnight at 15 C. The precipitated cholesterol is filtered, washed with water and ethanol and dried. 13.75 g. are recovered. The filtrate is concentrated to 60 m1. under vacuum, mixed with 75 ml. of water and extracted three times with chloroform. The extracts are washed with water, dried and evaporated under vacuum. The residue is taken up in 15 ml. of ether and allowed to stand overnight at 8 C. The crystals are filtered and washed with ether, whereby 11.2 g. of -cis-1,3-dibenzyl-hexahydrolH-furo 3,4-d] imidazole-2,4-dione are obtained. [a] =-|57.2 (c. =l in benzene).

EXAMPLE 2 Preparation of -cis-1,3-dibenzyl-lH-hexahydrothieno 3,4-d] imidazole-2,4-dione 50 g. of (+)-cis-1,3-dibenzyl-hexahydro-lH-furo[3,4- d]imidazole-2,4-dione are stirred with 20 g. of potassium thioacetate in 50 ml. of dimethylformamide for 10 minutes at 145 C. to 150 C. After work-up in accordance with Example 1, there are obtained 47.1 g. of (+)-cis- 1,3 dibenzyl 1H hexahydro-thieno[3,4-d]imidazole- 2,4-dione. [a] =+91.4- (c.=1 in CHC1 A further 0.7 g. is recovered from the mother liquors. [a] +893.

EXAMPLE 3 Preparation of )-cis-1,3-dibenzyl-hexahydro-1H- thieno[3,4-d]imidazole-2,4-dione 10 g. of (+)-cis-1,3-dibenzyl-hexahydro-lH-furo- [3,4-d]imidazole-2,4-dione, 12 ml. of quinoline and 4 g. of potassium thioacetate are stirred at 175 C. under nitrogen. At intervals of 30 minutes, two additional portions, each comprising 2 g. of potassium thioacetate, are added. After the last addition, the mixture is stirred for an additional 30 minutes at 175 C. After cooling the mixture, 100 ml. of benzene and 50 ml. of water are added. The benzene layer is removed by separation and successively washed with water, with 20% hydrochloric acid, and with water. The aqueous solutions are each extracted once again with benzene. The benzene solutions are evaporated to dryness under vacuum. The residue is crystallized in 50 ml. of isopropanol and there are obtained 7.05 g. of (+)-cis-1,3-dibenzyl-hexahydro-1H- thieno[3,4-d]imidazole-2,4-dione, having a melting point of 124 C.-125 C. [a] =+8=9.0 (c.=1 in CHCl By concentration of the mother liquor, there are obtained an additional 1.2 g., having a melting point of 122-124 C.; [a] -|86.6.

EXAMPLE 4 Preparation of )-cis-1,3-dibenzy1-hexahydro-1H- thieno[3,4-d]imidazole-2,4-dione 10 g. of (+)-cis 1,3 dibenzyl-hexahydro-IH-furo [3,4-d]imidazole-2,4-dione are reacted in analogous manner to Example 3, but in 10 ml. of diethylamine in place of quinoline. There are obtained 8.0 g. of (+)-cis- 1,3 dibenzyl-hexahydro 1H thieno[3,4-d]imidazo1e- 2,4-dione, having a melting point of 126-127 C. [a] =+90.i1 (c.= 1 in CI-ICI An additional 0.12 g. can be crystallized from the mother liquor.

EXAMPLE Preparation of -cis- 1, 3-dibenzyl-hexahydro- 1H- thieno[3,4-d]imidazole-2,4-dione g. of (+)-cis-1,3 dibenzyl hexahydro lH-furo [3,4-d]imidazole-2,4-dione are stirred with 4 g. of potassium thioacetate in 12 ml. of 2,4,6-trimethylpyridine at 175 C. for 1 /2 hours under nitrogen. After work-up in accordance with Example 1, there are obtained 6.9 g. of (+)-cis-1,3 dibenzyl hexahydro 1H thieno[3,4-d] imidazole-2,4-dione, having a melting point of 125 126 C.

EXAMPLE 6 Preparation of +)-cis-1,B-dibenzyl-hexahydro-IH- thieno[3,4-d]imidazole-2,4-dione 5 g. of cis 1,3 dibenzyl hexahydro-lH-furo [3,4-d]imidazole-2,4-dione, 2 g. of potassium thioacetate and 6 ml. of phenyl ethyl ether are stirred together at 175 C. under nitrogen. At intervals of 30 minutes, two

additional portions, each comprising 1 g. of potassium thioacetate, are added. After the last addition, the mixture is stirred at 175 C. for an additional 30 minutes. Thereupon, the reaction mixture is cooled, treated with ml. of benzene and washed three times with 100 ml. of water each time. The solvents are removed by distillation under vacuum. The residue is crystallized from isopropanol, whereby there are obtained 2.7 g. of (+)-cis- 1,3-dibenzyl-hexahydro-1H thieno[3,4 d]imidazole-2,4- dione; [a] =+86.1 (c.=1 in CHCl EXAMPLE 7 Preparation of (+)-cis-1,3-dibenzyl-hexahydro-1H- thieno [3 ,4-d] imidazole-2,4-di0ne 5 g. of (+)-cis-1,3-dibenzyl-hexahydro-lH-furo[3,4-d] imidazole-2,4-dione, 2 g. of sodium thioacetate and 6 ml. of diethylaniline are stirred together at C. under nitrogen. At intervals of 30 minutes, two additional portions, each comprising 1 g. of sodium thioacetate are added. After the last addition, the mixture is stirred at 175 C. for an additional 30 minutes. After cooling the reaction mixture, it is treated with water and benzene. The benzene extract is successively washed with 20% hydrochloric acid, with sodium bicarbonate solution, and with water. Thereupon, the benzene is removed by evaporation. The residue is crystallized from isopropanol whereby there are obtained 2.98 g. of (+)-cis-1,3-di'benzyl-hexahydrolH-thieno[3,4-d]imidazole-2,4-dione.

EXAMPLE 8 Preparation of )-cis-1,3-dibenzyl-hexahydro-1H- thieno [3,4-d] irnidazole-2,4-dione 10 g. of (+)-cis-1,3-dibenzyl hexahydro 1H furo [3,4-]imidazole-2,4-dione, 6.2 g. of potassium thiobenzoate and 10 ml. of dimethylacetamide are stirred together under nitrogen for 20 minutes at 140 C. The reaction mixture is Worked up in accordance with Example 1, whereby there are obtained 7.8 g. of (+)-cis-1,3-dibenzyl-hexahydro-IH thieno[3,4 d]imidazole-2,4-dione, having a melting point of 123 -124 C.

EXAMPLE 9 Preparation of -cis-1,3-dibenzyl-hexahydro-1H- thieno[3,4-d]imidazole-2,4-dione 5 g. of (+)-cis-1,3-dibenzyl-hexahydro-IH-furo[3,4-d] imidazole-2,4-dione and 2 g. of potassium thioacetate are heated at 171 to 181 C. in 100 ml. of carbon disulfide under nitrogen in a stirring autoclave for 12 hours. The reaction mixture is evaporated to dryness under vacuum and the residue is taken up in benzene and water. The phases are separated and the aqueous layer is once again extracted with benzene. The benzene extracts are Washed twice with saturated sodium chloride solution and subsequently evaporated to dryness under vacuum. The residue is crystallized from isopropanol, whereby there are obtained 3.62 g. of (+)-cis-1,3-dibenzyl-hexahydrolH-thieno[3,4-d]imidazole-2,4-dione, having a melting point of 124-126 C.

EXAMPLE 10 Preparation of (+)-cis-l,3-dibenzy1-hexahydro-1H- thieno[3,4-d]imidazole-2,4-dione 2.5 g. of (+)-cis-l,3-dibenzyl hexahydro lH-furo [3,4-d]imidazole2,4-dione and 1.0 g. of potassium thioacetate are stirred at 180 C. under nitrogen. Each 30, 60 and 90 minutes after the start of heating, three additional portions, each of 0.5 g. of potassium thioacetate are added. After /2 hour, the mixture is cooled. The reaction product is taken up in benzene and dilute hydrochloric acid, and the organic phase is washed neutral with water. The benzene is removed by distillation under vacuum and the residue crystallized from 25 ml. of isopropanol. There is obtained a first portion of 1.52 g. and,

11 after concentration of the mother liquor, a second portion of 0.12 g. of (+)-cis-1,3-dibenzyl-hexahydro-1H- thieno 3,4-d] imidazole-2,4-dione.

EXAMPLE 11 Preparation of racernic cis-1,3-dibenzyl-hexahydro-1H- thieno ['3 ,4-d] imidazole-2,4-dione 240 m1. of dimethylacetamide, 238 g. of racemic cis- 1,3 dibenzyl-hexahydro 1H furo[3,4-d]imidazole-2,4 dione and 95 g. of potassium thioacetate are heated to 150 C. for 30 minutes. The reaction mixture is cooled to 80 C. and 2.5 l. of benzene and, later, 2.5 l. of water are added. The layers are separated. The aqueous phase is extracted twice with 0.5 l. of benzene each time and the benzene extracts are combined and evaporated. The residue is dissolved hot in 600 ml. of isopropanol. After 12 hours at room temperature, there are obtained 215 g. of racemic cis-1,3-dibenzyl-hexahydro-1H-thieno[3,4-d] imidazole-2,4-dione, having a melting point of 127- 128 C.

EXAMPLE 12 Preparation of ([+)-biotin A solution containing Grignard reagent in 18.2 ml. of tetrahydrofuran is prepared at 6070 C. from 1.03 g. of magnesium turnings and 4.05 g. of 1-chloro-3-methoxypropane. The resulting solution is added dropwise to a solution, preheated to 45 C., of 10 g. of (:+)-cis-1,3-dibenzyl-hexahydro-lH-thieno[3,4-d] imidazole-2,4-dione in 110 ml. of toluene. The temperature rises to about 62 C. The mixture is allowed to cool to room temperature over a period of 2 hours, and then with ice-cooling, 22 ml. of water and 5.5 ml. of concentrated hydrochloric acid are added. The layers are separated. The aqueous phase is again extracted with toluene and the organic extracts are repeatedly washed with water. The combined toluene extracts are diluted with 25 ml. of methanol, made alkaline (pH 11) with 28% aqueous sodium hydroxide solution and allowed to stand at room temperature for 30 minutes. The reaction mixture is treated with water. The aqueous phase is separated and repeatedly extracted with toluene. The toluene extracts are washed neutral with water, dried and evaporated to dryness in vacuum, whereby there are obtained 9.98 g. of +)-cis-1,3-dibenzyl-4-hydroxy-4-(3- methoXypropyD-hexahydro 1H thieno[3,4-d1imidazol- 2-one, which can be crystallized from acetone-ether-petroleum ether, and has a melting point of 114-116 C.

[a]; -=y+89.2 (c. =1.0 in CHCl The 9.98 g. of product are boiled at reflux in 100 m1. of glacial acetic over a period of 2 hours. The glacial acetic is distilled under vacuum. The residue is taken up in benzene and this solution is washed with sodium bicarbonate solution and with water. After evaporation of the solvent, there are obtained 9.45 g. of cis-1,3-dibenzyl-4- (3-methoxypropylidene)-hexahydro 1H thieno[3,4-d] imidazol-Z-one; [a] .=;+222 (c.=1 in CHCI This compound is dissolved in 56 ml. of methanol and hydrogenated in the presence of about 9 g. of Raneynickel at 35 to 40 C. under about 40 atmospheres of hydrogen pressure. After removal of the catalyst, the solution is evaporated under vacuum, whereby there are obtained 8.6 g. of (-)-cis-1,3-dibenzyl-4-(3-methoxypropyl)-hexahydro-thieno[3,4-d]imidazol-2-one as an oil. [a] 42.4 (c.'=1.0 in CHCl This compound is heated to 90-95 C. with 14.5 ml. of 48% aqueous hydrobromic acid with intensive stirring for 2 hours. A brownish colored solution forms which is cooled and extracted with toluene. The aqueous phase is evaporated under vacuum. The residue is taken up with 50 ml. of acetone, whereby 6.78 g. of ()-cis, cis-1,3- dibenzyl-decahydro-imidazo[4,5 c]thieno[1,2 a]thilium bromide crystallize out, having a melting point of (dec.) 206-207 [a] =-I8.O (c.=1.0 in methanolwater 1:1). An additional 0.23 g. of the product is ob- 12 tained in crystalline form by concentration of the mother liquors.

8.74 g. of malonic acid diethyl ester are added dropwise to a suspension containing 2.2 g. of sodium methylate in 40 ml. of toluene heated to C. The mixture is stirred at 80 C. for 1 hour, cooled to 60 C. and 6.16 g. of ()-cis, cis 1,3 dibenzyl-decahydro-imidazo[4,5-c] thieno[1,2-a] thiolium bromide are added. The mixture is heated at reflux for 3 hours. Then, it is cooled to room temperature, 20 ml. of water are added thereto and the phases are separated. The organic phase is dried and the solvent removed under vacuum. With stirring, the residue is heated to boiling with ml. of 48% hydrobromic acid. Ethyl bromide, acetic acid and benzyl bromide which are formed in the course of the reaction are removed by distillation together with a smaller amount of aqueous hydrobromic acid. The reaction mixture is heated to to 126 C. for 3- /2 hours. Then, the aqueous hydrobromic acid is removed under vacuum. The residue is boiled in 90 ml. of water. The hot solution is decanted from the oily insoluble material, cooled and allowed to stand overnight in a refrigerator. The crystals of crude ({.+)-biotin are filtered and washed with water and with acetone, whereby there is obtained (+)-biotin, which is recrystallized from water, and has a melting point of 230-232 C. [oz] +90i1 (c.'=1 in 0.1 N NaOH).

EXAMPLE 13 Preparation of )-bi0tin 11.0 g. of magnesium are covered with 70 ml. of diethyl ether and 70 ml. of toluene. A solution containing 24.9 g. of 1,2-dibromoethane in 36 ml. of diethyl ether is then added dropwise with cooling over a period of about 20 minutes. Temperature of the reaction mixture is 20 to 28 C. After 45 minutes, a solution of 16.9 g. of 1,4-dichlorobutane in 36 ml. of diethyl ether and 75 ml. of toluene is added dropwise over a period of 25 minutes. The mixture is stirred for an additional 105 minutes. The suspension obtained is cooled to -30 to -40 C. and a solution of 14.65 g. of (+)-cis-1,S-dibenzyl-hexahydrothieno [3,4-d]imidazole-2,4-dione in 260 ml. of toluene is added dropwise at this temperature. The mixture is stirred for an additional 1 hour at 30 to 40 C. and then carbon dioxide is led in firstly for 1 hour at 30 to 40 C. and thereafter for 1 hour at room temperature.,Then, the reaction mixture is decomposed with ice and hydrochloric acid. The organic phase is separated, washed with water and evaporated to dryness. The residue is shaken over a period of 40 minutes with m1. of 5% sodium carbonate solution. Undissolved neutral portions are extracted with ethylacetate. The aqueous solution is acidified to a pH 5.5 with hydrochloric acid and extracted with ethyl acetate. The ethyl acetate extracts are washed with water, dried and evaporated under vacuum, whereby there are obtained 13.28 g. of crude cis-5-(1,3-dibenzyl-4-hydroxy- 2-keto-hexahydro-1H-thieno[3,4-d]imidazolyl 4)valeric acid as an oil which is dextrorotatory in chloroform. 11.6 g. of this oil are boiled at reflux in 60 ml. of glacial acetic over a period of 2 hours. The glacial acetic is removed by distillation under vacuum. The residue is dissolved in toluene and evaporated under vacuum. The residual, oily cis-1,3-dibenzyl-4-(4 carboxybutylidene)-hexahydro-1H- thieno[3,4-d]imidazol-2-one which is dextrorotatory in chloroform is dissolved in 80 ml. of methanol and hydrogenated in the presence of Raney-nickel at 3540 C. under 38 to 40 atmospheres of hydrogen pressure. The catalyst is removed by filtration, and the filtrate is evaporated, whereby there are obtained 10.3 g. of oily crude N,N-dibenzyl-biotin, which is levorotatory in chloroform.

10.3 g. of crude N,N-dibenzyl-biotin are heated at reflux 'for 5 hours in 100 ml. of 48% hydrobromic acid. 60 ml. are then distilled under partial vacuum. The remaining solution is diluted with 230 ml. of water and boiled at reflux for 10 minutes. The hot solution is decanted from a dark-brown insoluble oil. The oil is again thoroughly boiled with 80 ml. of water and decanted, whereby there remain 2.9 g. of oil as an insoluble residue. The aqueous solutions are combined, concentrated to 50 ml. and allowed to stand at C. for 24 hours, whereby there crystallize 0.61 g. of (+)-biotin, having a melting point of 225228 C.; [u] =-|-86.0 (c.=1.0 in 0.1 N NaOH). The filtrate is evaporated to dryness and once more boiled at reflux for 3 /2 hours in 100 ml. of 48% hydrobromic acid. The hydrobromic acid is removed under vacuum and the residue taken up in 5-0 ml. of water. After 24 hours at +5 C. there crystallize 0.72 g. of biotin, having a melting point of 223 -225 C.; [u] =-+83.2 (c.'=1.0 in 0.1 N NaOH). The filtrate is treated with 2 g. of sodium carbonate. Phosgene is introduced into the solution at about C. up to pH 1. 0.58 g. of (+)-biotin crystallizes from the reaction mixture overnight, and has a melting point of 224-226 C. [a] =-|85.5 (c.=1.0 in 0.1 N NaOH).

EXAMPLE 14 Preparation of (+)-biotin A solution of a Grignard reagent, prepared in 6 5 ml. of ether from 1.8 g. of magnesium and 9.18 g. of 4-bromol-methoxybutane, is added dropwise over a period of 20 minutes to a solution, heated to 50 C., of 16.9 g. of )-cis 1,3-dibenzyl-hexahydrolH-thieno 3,4-d] imidazole-2,4-dione in 200 ml. of benzene. The solution is stirred for an additional hour and then cooled. The reaction mixture is decomposed with ice and dilute hydrochloric acid. The organic phase is separated and Washed neutral with water. After distillation of the solvent under vacuum, 23.7 g. of cis 1,3 dibenzyl 4 hydroxy-4- (4 methoxybutyl)-hexahydro-1H-thieno[3,4-d]imidazol- 2-one are obtained as an oil. The oil is boiled at reflux in a mixture comprising 200 ml. of methanol and 2 ml. of concentrated sulfuric acid for 1 hour. The methanol is distilled under vacuum and the residue is taken up in benzene and water. The benzene solution is washed neutral, dried and evaporated to dryness, whereby there are obtained 21.4 g. of cis-1,3-dibenzyl-4-(4-methoxybutylidene)-hexahydro lH-thieno[3,4-d]imidazol-2-one as an oil which is dextrorotatory in benzene. 16.1 g. of the oil are dissolved in 160ml. of methanol and hydrogenated in the presence of about 30' g. of Raney-nickel under 25 to 30 atmospheres of hydrogen pressure. The catalyst is removed by filtration and the methanol distilled under vacuum. The residue is crystallized from isopropyl ether, whereby there are obtained 11.6 g. of ()-cis-1,3-dibenzyl 4- (4-methoxybutyl) -hexahydro-1H-thieno 3,4-d] imidazol-Z-one, having a melting point of 87-89 C. [m] =41.4 (c.'=1 in benzene).

10 g. of ()-cis-1,3-dibenzyl-4-(4-methoxybutyl)- hexahydro-lH-thieno[3,4-d]imidazol-Z-one are dissolved in 100 ml. of a 33% solution of hydrobromic acid in glacial acetic and allowed to stand at room temperature for 60 hours. The mixture is evaporated to dryness under vacuum. The residue is taken up in benzene and the solution is repeatedly washed with water, dried over sodium sulfate and chromatographed through 150 g. of aluminum oxide of activity III. 8.4 g. of substance are eluted with benzene. After the eluate is dissolved in isopropyl ether, there crystallize 5.0 g. of ()-cis-1,3-dibenzyl-4-(4-bromobutyD-hexahydro 1H thieno[3,4-d]imidazol-2-one, having a melting point of 787,9 0.; [a] =49.7 (c.=1 in benzene). 5.0 g. of ()-cis-1,3-dibenzyl4 (4 bromobutyl)-hexahydro-1H-thieno[3,4-d]imidazol-2- one are dissolved in 25 ml. of dimethyl sulfoxide and stirred with 1.53 g. of sodium cyanide for 3 hours at 80 C. After cooling the reaction mixture, benzene and Water are added thereto. The phases are separated, and the benzene solution is repeatedly washed with water. Following evaporation of the solvent under vacuum, the residue is dissolved in isopropanol. After the addition of n-hexane, 4.35 g. of ()-cis-1,3-dibenzyl-4-(4-cyanobutyl)-hexahydro-1-H-thieno[3,4-d1imidazol-2 one crystallize overnight and has a melting point of 97 C. [a] =56.8 (c. =1 in benzene).

4.25 g. of ()-cis-N,N-dibenzyl-biotin-nitrile are heated to the boiling temperature with m1. of 48% hydrobromic acid for 3 hours, and the benzyl bromide which forms is continuously removed by distillation. The reaction mixture is extracted with benzene. The aqueous phase is evaporated under vacuum. The residue is dissolved hot in 300 m1. of water and extracted hot with 1,2- dichloroethane. The aqueous solution is concentrated, and there are obtained two portions of 1.25 g. and 0.30 g. of (+)-biotin.

EXAMPLE 15 Preparation of (-)-cis-1,3-dibenzy1-4-(4-bromobutyl)- hexahydrolH-thieno 3,4-d] imidazol-Z-one A solution of a Grignard reagent is prepared by reacting 7.5 g. of magnesium with 49.5 g. of 4-benzyloxyl-chlorobutane in 95 ml. of tetrahydrofuran over a period of 50 minutes at about 70 C. 84 ml. of the solution are added dropwise to a solution, preheated to 50 C. of 33.8 g. of (+)-cis-1,3-dibenzyl-hexahydro-lH-thieno- [3,4-d]imidazole-2,4-dione in 300 ml. of tetrahydrofuran. Subsequently, the temperature is maintained at 60 C. for 1% hours. Then, the solution is concentrated under vacuum. The residue is treated with toluene, ice and ammonium chloride solution. The organic phase is washed with water. After evaporation of the solvent, there are obtained 60.7 g. of crude (-)-cis-1,3-dibenzyl-4-(4-benzyloxybutyl) 4 hydroxy-hexahydro 1H thieno- [3,4-d]imidazol-2-one which may be crystallized from ether, and has a melting point of 89-90 C. [a] =-5.5 (c.=1 in benzene).

30 g. of ()-cis-1,3 dibenzyl 4 (4-benzyloxybutyl)- 4-hydroxy-hexahydrolH-thieno 3,4-d] imidazol-Z-one are dissolved in 200 ml. of methanol and, after the addition of 2.5 ml. of concentrated sulfuric acid, boiled at reflux for 1 hour. Subsequently, the mixture is neutralized with sodium bicarbonate, filtered and the filtrate evaporated, whereby 26.1 g. of ('+)-cis-1,3-dibenzyl-4-(4-benzyloxybutylidene)-hexahydro-lH-thieno[3,4-d]imidazo1-2 one are obtained as an oil which is dextrorotatory in benzene solution. The oil is dissolved in ml. of methanol and hydrogenated in the presence of about 20 g. of Raney nickel under 35 atmospheres of hydrogen pressure up to 40. The catalyst is removed by filtration and the filtrate evaporated to dryness under vacuum, whereby 24 g. of ('-)-cis 1,3-di-benzyl-4-(4-benzyloxybutyl)-hexahydro- 1H-thieno[3,4-d]imidazol-2-one are obtained as an oil which is levorotatory in benzene. In an analogous manner to Example 14, this is converted to ()-cis-1,3-dibenzyl- 4 (4 bromobutyD-hexahydro 1H thieno[3,4-d] imidazol-Z-one and then further to (+)-biotin.

We claim:

1. (+)-'Cis 1,3 dibenzyl-hexahydro-lH-thieno[3,4- d] imidazole-2,4-dione.

.2. A process for the preparation of a racemic or optically active (+)-thiolactone of the formula wherein rings A and B are cis-linked, and R is benzyl, which comprises reacting, at a temperature in the range of from about 100 C. to about 200 C., a racemic or optically active (+)-lactone of the formula References Cited UNITED STATES PATENTS Surmatis et a1. 260309.7 Goldberg et a1. 260309.7 Goldberg et a1. 260309.7 Goldberg et a1. 260309.7

Goldberg et a1. 260309.7

1 6 OTHER REFERENCES The Merck Index, 8th ed., page 1040, Rahway, N.J., Merck & Co., 1968.

Handbook of Chemistry and Physics, 44th ed., page 5 858, Cleveland, Ohio, Chem. Rubber Pub., 1961.

Dyke: The Chemistry of the Vitamins, pages 16181, N.Y., Interscience-Wiley, 1965.

Elderfield: Heterocyclic Compounds, vol. 1, pages 268- 76, N,Y., Wiley, 1950.

Gerecke et al.: Chem. Abst., vol. 73, No. 56027p (1970).

Gerecke et al.: (Gerecke, Zimmermann and Aschwanden), I-Ielv. Chim. Acta, 1970, vol. 53, pages 991-9 (July 10, 1970).

Ing et al.: Vitamine Chemie und Biochemie, pages 555-69, Gustav Fischer Verlag Jena, 1964.

Isaka et al.: Chem. Abst., vol. 70, No. 11632d (1969).

Isaka et al.: J. Pharm. Soc. (Japan), vol. 88, pages 1062-7 (1968).

Drug Trade News, Feb. 21, 1949, page 40.

NATALIE TROUSOF, Primary Examiner U. S. Cl. X.R. 

